how to get Freeman chain code in OpenCV C++?

Question

I have this code for contour detection and I also need to display the Freeman chain code, but for some reason it's not working and I don't really know how to fix it.

#include<opencv2/opencv.hpp>
#include <iostream>
#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc/imgproc_c.h"

#define CV_READ_SEQ_ELEM(elem, reader)

using namespace std;
using namespace cv;

int main() {
    // read the image
    Mat image = imread("C:/Users/Admin/Downloads/img.jpg");

    // convert the image to grayscale format
    Mat img_gray;
    cvtColor(image, img_gray, COLOR_BGR2GRAY);

    // apply binary thresholding
    Mat thresh;
    threshold(img_gray, thresh, 150, 255, THRESH_BINARY);
    imshow("Binary mage", thresh);
    waitKey(0);
    imwrite("image_thres1.jpg", thresh);
    destroyAllWindows();

    // detect the contours on the binary image using cv2.CHAIN_APPROX_NONE
    vector<vector<Point>> contours;
    vector<Vec4i> hierarchy;
    findContours(thresh, contours, hierarchy, RETR_TREE, CHAIN_APPROX_NONE);
    // draw contours on the original image
    Mat image_copy = image.clone();
    drawContours(image_copy, contours, -1, Scalar(0, 255, 0), 2);
    imshow("None approximation", image_copy);
    waitKey(0);
    imwrite("contours_none_image1.jpg", image_copy);


    //find chain code

    vector<vector<Point> > contours;

    findContours(image_copy, contours, RETR_EXTERNAL, CV_CHAIN_CODE);
    cout << Mat(contours[0]) << endl;

    findContours(image_copy, contours, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE);
    cout << "CHAIN_APPROX_SIMPLE" << endl;
    cout << Mat(contours[0]) << endl;

    CvChain* chain = 0;
    CvMemStorage* storage = 0;
    storage = cvCreateMemStorage(0);
    cvFindContours(&Mat(image_copy), storage, (CvSeq**)(&chain), sizeof(*chain), CV_RETR_EXTERNAL, CV_CHAIN_CODE);

    for (; chain != NULL; chain = (CvChain*)chain->h_next)
    {
        //chain=(CvChain*)chain ->h_next; 
        //if(chain==NULL){break;}
        CvSeqReader reader;
        int i, total = chain->total;
        cvStartReadSeq((CvSeq*)chain, &reader, 0);
        printf("--------------------chain\n");

        for (i = 0; i < total; i++)
        {
            char code;
            CV_READ_SEQ_ELEM(code, reader);
            printf("%d", code);
        }
    }


    destroyAllWindows();

}

These are the errors that I get when I try to run the code in Visual Studio:

Build started...
1>------ Build started: Project: Lab1_PI, Configuration: Debug x64 ------
1>chain_code.cpp
1>C:\Users\Admin\source\repos\Lab1_PI\Lab1_PI\chain_code.cpp(7,1): warning C4005: 'CV_READ_SEQ_ELEM': macro redefinition
1>C:\Users\Admin\Downloads\opencv\build\include\opencv2\core\types_c.h(1916): message : see previous definition of 'CV_READ_SEQ_ELEM'
1>C:\Users\Admin\source\repos\Lab1_PI\Lab1_PI\chain_code.cpp(39,25): error C2086: 'std::vector<std::vector<cv::Point,std::allocator<cv::Point>>,std::allocator<std::vector<cv::Point,std::allocator<cv::Point>>>> contours': redefinition
1>C:\Users\Admin\source\repos\Lab1_PI\Lab1_PI\chain_code.cpp(29): message : see declaration of 'contours'
1>C:\Users\Admin\source\repos\Lab1_PI\Lab1_PI\chain_code.cpp(51): error C2102: '&' requires l-value
1>Done building project "Lab1_PI.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

If anyone knows how to fix it, I would be very grateful.